A phase frequency detector (PFD) is an electronic circuit that compares the phase and frequency of a first signal to that of a reference signal. Based on the comparison, the PFD generates one or more control signals. In phase-locked loop (PLL) implementations, the PFD generates the one or more control signals to control a charge pump. The charge pump is used to generate a control voltage for controlling the frequency of oscillation of a voltage-controlled oscillator (VCO). In some PLL designs, e.g., fractional-N PLLs, charge pump nonlinearities arising from mismatched charge pump currents introduce a significant amount of phase noise in the loop, which degrades the PLL performance.